The NATO command in Afghanistan is investigating the deaths of five civilians during a skirmish Tuesday in the south.
The incident occurred in the Sangin district of Helmand province, the volatile region where fighting has raged for years.
The International Security Assistance Force said insurgents with small arms and machine guns assaulted coalition forces.
After troops identified the attackers' positions, they fought back "with direct and indirect fire."
"This is a tragedy," said ISAF spokesman U.S. Army Lt. Col. Patrick Hynes. He said the military is aware that "insurgents purposefully stage attacks against friendly forces" based in the homes of innocent civilians.
The deaths of civilians during fighting have hurt the coalition's efforts to win backing for its efforts, and the forces in recent years have worked to lessen such casualties.
Also on Tuesday, two coalition service member died in the south, both after bombing attacks, ISAF said. The precise locations of the killings and the nationalities of the service members were not immediately made available.
Also, over the previous 24 hours, an ISAF and Afghan border police patrol found 992 pounds of hashish in the Spin Boldak district of Kandahar province, also in the south.
In the same district, a police patrol found 33,000 pounds of ammonium nitrate, which is used to make explosives, and approximately 1,322 pounds hashish. Several people were detained.